The present invention relates, in general, to multiple operator, semiautomatic welding systems, and more particularly to systems capable of handling two different types of welding operations from a single power supply.
Multiple operator welding power sources, which serve from a single power supply a plurality of welding operators using stick electrodes, have been well known for many years. Such systems eliminate the necessity of having separate power sources at each welding location by providing individual resistor grids linked to one central power supply. A constant potential power supply is placed at a central location convenient to all of the operators, with only the individual resistor grids, associated cables, and electrode holders, being at the work site. The resistor grids each comprise a tapped series resistor box convenient to the operator who selects the desired welding current for his particular job. Such systems have provided real savings in both time and effort for those who use, store, and transport such equipment, for a single multiple-operator power source with several small resistance control grids is lighter, smaller, less cumbersome and less expensive to install and operate than the equivalent number of power supplies formerly used.
Early attempts to design constant potential multiple operator units for use with gas-metal arc welding; i.e., arc welding utilizing a gas-shielded consumable electrode, had several shortcomings, particularly when used in the semiautomatic, operator-held mode. First, the fluctuations in the main line voltages caused undesirable arc voltage drift, and second, the switching on and off of other arcs caused further undesirable arc voltage disturbances. Recent improvements, have resulted in power sources which are capable of usage by multiple operators, while minimizing arc voltage disturbances and drift to provide satisfactory results in gas-metal arc welding with either solid or fluxcored wires. For successful use of the multiple operator concept, however, it is necessary that all arcs operate satisfactorily from the power supply unit, and this has created a difficulty in that the presently available power supplies lack the versatility required for application to short-circuiting arc operations, wherein the arc is characterized by a series of repetitive short circuits between the consumable electrode wire and the workpiece.